You know when I do IOtD you're subjected to whatever blows my skirt up. This picture did.
I found this picture of UK food rationing in 1943, this is a weeks rations for two people… it got worse.

Intrigued by the picture, I started looking into it. Starting in January of 1940 with bacon, butter, and sugar, more and more
things were added as the war dragged on. Just before VE day it was cut again and it took until 1954 to end completely.
There were special supplement rations for certain hard working occupations but they were very small. Diabetics got more butter
and meat but gave up sugar coupons. Vegetarians got more cheese but gave up meat coupons. Everybody was growing gardens.

In 1939 the University of Cambridge did a secret study to determine the minimum people could live on and stay health with
fairly rigorous activity. They established guidelines but found it took a long time to prepare and eat, plus what they described
as a "remarkable" increase in flatulence from the high amount of starch in the diet, plus a 250% increase in poop.

They established guidelines but found it took a long time to prepare and eat, plus what they described as a "remarkable" increase in flatulence from the high amount of starch in the diet, plus a 250% increase in poop.

Any major dietary change will result in a huge amount of flatulence for a few weeks, because it's caused (among other things) by mass bacterial die-off. You're starving the bacteria that eat what you used to eat, while growing the colonies that eat what you're now eating. The farting from a newly-high-starch diet will go away after awhile, and then would come back with a vengeance if/when you switched back to a relatively starchless diet. The same is partially true of poop quantities--the efficiency of our metabolism and how much we're able to utilize from a given meal has to do with the colonies we've cultivated. Give it a few months, and the more efficient colonies will thrive and the poop quantity will go down again. This is, of course, independent from certain generally-more-or-less digestible foods with variable fiber content, fermentable sugar content, etc. But radical shifts in diet play at least a partial role in the output of one's butthole.